An interior view of a supermarket is seen after an explosion in St Petersburg, Russia, in this photo released by Russia’s National Anti-Terrorism Committe on December 28, 2017. National Anti-Terrorism Committe/Handout via REUTERS

MOSCOW (Reuters) - Russia’s Investigative Committee said on Sunday it had indicted on terrorism charges a suspect who allegedly organised and carried out a bombing that injured 13 people in a St. Petersburg supermarket this week.

The committee said in a statement that the suspect, whose identity has not been disclosed by investigators, “deliberately made and planted a homemade explosive device” that exploded on Wednesday at a branch of the Perekrestok supermarket chain in Russia’s second city.

The suspect told investigators he had been motivated by “hatred toward the organisers and participants” of mindset training sessions he used to attend, the committee said without providing further detail.

Investigators said the suspect had also hidden two USB drives near the site of the blast containing information about his actions and photographs of the explosive device.

The suspect will undergo psychological testing to assess his sanity. Investigators said has been followed by mental health professionals since the age of 19 for undisclosed issues. The indictment did not say how old he is now.

The Islamic State militant group claimed responsibility for the blast but did not provide evidence to support its assertion.

The claim came after Russian President Vladimir Putin said the explosion, caused by what investigators said was a homemade bomb packed with pieces of metal, was an act of terrorism.